Process for producing a shaped article from contact material based on silver, contact material and shaped article

Abstract

A contact material, a shaped article or contact piece and a process for producing a shaped article from a contact material based on silver, include forming a powder mixture from silver and a metal oxide, and metallurgically processing the powder to form the shaped article with the metal oxide being reduced to metal. Since metal oxide powders are obtainable with a very much smaller particle size than metal powders, it is possible to obtain a contact material with a mean particle size of the metal incorporated as an active component of less than 1 μm. Such a contact material has particularly favorable switching properties as a result of the fine particle size.

We claim: 
     
       1. A process for producing a shaped article from a contact material based on silver, which comprises: forming a powder mixture from silver and a metal oxide; and   processing the powder mixture by powder metallurgy to form a shaped article with the metal oxide completely reduced to metal.   
     
     
       2. The process according to claim 1, which comprises carrying out the step of reducing the metal oxide in the powder mixture. 
     
     
       3. The process according to claim 1, which comprises carrying out the step of reducing the metal oxide in a blank of the shaped article. 
     
     
       4. The process according to claim 1, which comprises carrying out the step of reducing the metal oxide by heat treatment in a reducing atmosphere. 
     
     
       5. The process according to claim 4, which comprises carrying out the heat treatment at a temperature of 500 to 1000° C. 
     
     
       6. The process according to claim 4, which comprises carrying out the heat treatment at a temperature of 700° C. 
     
     
       7. The process according to claim 4, which comprises carrying out the heat treatment in a hydrogen (H 2 ) reducing atmosphere. 
     
     
       8. The process according to claim 1, which comprises selecting a powder with a particle size of less than 1 μm, as the metal oxide. 
     
     
       9. The process according to claim 1, which comprises selecting a powder with a particle size of between 100 and 500 nm, as the metal oxide. 
     
     
       10. The process according to claim 1, which comprises mixing a material selected from the group consisting of a further metal and a further metal oxide, with the powder mixture. 
     
     
       11. The process according to claim 1, which comprises mixing a material selected from the group consisting of: silver (Ag), iron oxide (Fe 2  O 3  /Fe 3  O 4 ) and rhenium (Re);   silver (Ag), rhenium oxide (ReO) and iron; and   silver (Ag), rhenium oxide (ReO) and iron oxide (Fe 2  O 3  /Fe 3  O 4 );   with the powder mixture.   
     
     
       12. In a contact material based on silver, the improvement comprising at least one further metallic component formed of at least one material selected from the group consisting of iron (Fe) and rhenium (Re) and having a mean particle size less than 1 μm. 
     
     
       13. The contact material according to claim 12, wherein said mean particle size is between 100 and 500 nm. 
     
     
       14. The contact material according to claim 12, wherein said iron (Fe) is present in a proportion by mass of between 1% and 50% and said rhenium (Re) is present in a proportion by mass of between 0.01% and 5%. 
     
     
       15. A shaped article, comprising a contact material based on silver, and at least one further metallic component formed of at least one material selected from the group consisting of iron (Fe) and rhenium (Re) and having a mean particle size less than 1 μm. 
     
     
       16. The shaped article according to claim 15, wherein said mean particle size is between 100 and 500 nm. 
     
     
       17. The shaped article according to claim 18, wherein said iron (Fe) is present in a proportion by mass of between 1% and 50% and said rhenium (Re) is present in a proportion by mass of between 0.01% and 5%. 
     
     
       18. A contact piece for power engineering switching equipment, in particular for a low-voltage switch, comprising a contact material based on silver, and at least one further metallic component formed of at least one material selected from the group consisting of iron (Fe) and rhenium (Re) and having a mean particle size less than 1 μm.